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Clinical Outcomes Following Letrozole Treatment according to Estrogen Receptor Expression in Postmenopausal Women: LETTER Study (KBCSG-006)

 Sung Gwe Ahn  ;  Seok Jin Nam  ;  Sei Hyun Ahn  ;  Yongsik Jung  ;  Heung Kyu Park  ;  Soo Jung Lee  ;  Sung Soo Kang  ;  Wonshik Han  ;  Kyong Hwa Park  ;  Yong Lai Park  ;  Jihyoun Lee  ;  Hyun Jo Youn  ;  Jun Hyun Kim  ;  Youngbum Yoo  ;  Jeong Yoon Song  ;  Byung Kyun Ko  ;  Geumhee Gwak  ;  Min Sung Chung  ;  Sung Yong Kim  ;  Seo Heon Cho  ;  Doyil Kim  ;  Myung Chul Chang  ;  Byung In Moon  ;  Lee Su Kim  ;  Sei Joong Kim  ;  Min Ho Park  ;  Tae Hyun Kim  ;  Jihyoung Cho  ;  Cheol Wan Lim  ;  Young Tae Bae  ;  Gyungyub Gong  ;  Young Kyung Bae  ;  Ahwon Lee  ;  Joon Jeong 
 JOURNAL OF BREAST CANCER, Vol.24(2) : 164-174, 2021-04 
Journal Title
Issue Date
Breast neoplasms ; Letrozole ; Postmenopause ; Receptors, estrogen
Purpose: In this trial, we investigated the efficacy and safety of adjuvant letrozole for hormone receptor (HR)-positive breast cancer. Here, we report the clinical outcome in postmenopausal women with HR-positive breast cancer treated with adjuvant letrozole according to estrogen receptor (ER) expression levels.

Methods: In this multi-institutional, open-label, observational study, postmenopausal patients with HR-positive breast cancer received adjuvant letrozole (2.5 mg/daily) for 5 years unless they experienced disease progression or unacceptable toxicity or withdrew their consent. The patients were stratified into the following 3 groups according to ER expression levels using a modified Allred score (AS): low, intermediate, and high (AS 3-4, 5-6, and 7-8, respectively). ER expression was centrally reviewed. The primary objective was the 5-year disease-free survival (DFS) rate.

Results: Between April 25, 2010, and February 5, 2014, 440 patients were enrolled. With a median follow-up of 62.0 months, the 5-year DFS rate in all patients was 94.2% (95% confidence interval [CI], 91.8-96.6). The 5-year DFS and recurrence-free survival (RFS) rates did not differ according to ER expression; the 5-year DFS rates were 94.3% and 94.1%in the low-to-intermediate and high expression groups, respectively (p = 0.6), and the corresponding 5-year RFS rates were 95.7% and 95.4%, respectively (p = 0.7). Furthermore, 25 patients discontinued letrozole because of drug toxicity.

Conclusion: Treatment with adjuvant letrozole showed very favorable treatment outcomes and good tolerability among Korean postmenopausal women with ER-positive breast cancer, independent of ER expression.

Trial registration: ClinicalTrials.gov Identifier: NCT01069211.
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1. College of Medicine (의과대학) > Dept. of Surgery (외과학교실) > 1. Journal Papers
Yonsei Authors
Ahn, Sung Gwe(안성귀) ORCID logo https://orcid.org/0000-0002-8778-9686
Jeong, Joon(정준) ORCID logo https://orcid.org/0000-0003-0397-0005
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